Abstract: Objective To analyze the impact of low-dose esketamine combined with sufentanil on peri-operative inflammation and immune function of elderly patients undergoing total hip arthroplasty (THA). Methods From January 2019 to January 2022, 120 elderly patients who underwent THA under combined spinal-epidural anesthesia and received patient-controlled intravenous analgesia (PCIA) were included. The patients were divided into a control group (analgesic drugs: sufentanil + granisetron) and an observation group (analgesic drugs: esket- amine + sufentanil+granisetron). Pain intensity was assessed using the Visual Analog Scale (VAS). Serum level of interleukin (IL)-6, tumor necrosis factor (TNF)-α and C-reactive protein (CRP) was measured by ELISA. CD4⁺ and CD8⁺ cells were detected using a CytoFLEX flow cytometer, and the CD4⁺/CD8⁺ ratio was calculated. The incidence of adverse reactions in both groups was recorded and compared. Results In resting state, the post-surgical VAS scores in the observation group patients were significantly lower than those in control group at 48 and 72 h. In the active state, the VAS scores recorded for the observation group following surgery remained notably lower than those of the control group at 24, 48, 72 h (P＜0.05). Compared with 24 h before surgery in the same group, the level of IL-6, TNF-α, and CRP in the control group significantly increased at 24, 48, and 72 h after surgery, while in the observation group, they increased at 24 and 48 h after surgery and returned to pre-operative level at 72 h (P＜0.05). The observation group exhibited significantly lower level of IL-6, TNF-αand CRP as compared to the control group over the 24, 48, 72 h following surgery(P＜0.05). Compared with 24 h before surgery in the same group, CD8⁺ (%) increased, while CD4⁺ (%) and CD4⁺/CD8⁺ decreased in the observation group at 24, 48, and 72 h after surgery. However, 72 h after surgery, these values returned to the level before operation. Twenty four, 48, and 72 h after surgery, the observation group displayed notably elevated level of CD8⁺(%), CD4⁺(%) and CD4⁺/CD8⁺ as compared to the control group(P＜0.05). No significant variation in the occurrence of adverse reactions was observed between the two groups. Conclusions Low-dose esketamine combined with sufentanil can reduce peri-operative inflammation in elderly patients undergoing THA with minimal impact on immune function.

Key words: esketamine, sufentanil, total hip arthroplasty, immune function, inflammation